TABLE 4.

Mass, surface area and particle concentration as cellular dose metric, based on administered and deposited doses for all particles dispersed in SABM

Material	Effective density, ρe (g/cm3)	Deposition fraction constant, α (h−1)	t90 (h)	Administered dose at t = 24 h		Delivered dose at t = 24 h
				Mass (μg/ml)	SA (cm2)	Mass (μg)	SA (cm2)	Particles /cm2
PEPs PM0.1	2.39	0.027	85.2	0.5	3.29E + 04	0.5	1.57E + 04	7.22E + 12
PEPs PM2.5	3.10	0.016	143.9	0.5	4.19E + 04	0.5	1.34E + 04	7.97E + 12
TNEPs PM0.1	1.148	0.02	99.0	0.5	9.23E + 04	0.19	3.94E + 04	1.57E + 13
TNEPS PM0.1–2.5	1.141	0.03	83.3	0.5	7.01E + 04	0.25	3.4E + 04	7.69E + 12

The dose estimates derived from the VCM-ISDD model calculations.

SA, Surface area.

Note Surface area and particle number concentration dose metrics are based on VCM-ISDD model calculations. RID functions can be calculated by inserting appropriate alpha parameter, effective density and hydrodynamic diameter reported in Table 3 into Equations (3)–(5) as below for delivered mass, surface area, and particle number after a given exposure duration. The table reports the RID functions for 24 h exposure duration of PEPs and TNEPs.

For delivered to cell mass (RID_M, µg):

$${\text{RID}}_M=\left(1-e^{-\alpha t}\right)\times M.$$ (3)

For delivered to cell particle number (RID_N, number of particles).

$${\text{RID}}_N=\left(1-e^{-\alpha t}\right)\times N.$$ (4)

For total delivered to cell surface area (RID_SA, cm²),

$${\text{RID}}_{SA}=\left(1-e^{-\alpha t}\right)\times SA.$$ (5)